A DC-DC converter circuit is a combination of an inverter circuit, an output transformer, and a rectification circuit, and inverter circuits that are well known from the prior art are the full bridge type, the half bridge type, and the center tap push-pull type. FIG. 1 is a figure showing the concepts of these circuits.
The full bridge type includes switching elements S1 through S4 connected as a bridge, and a power supply V is connected over the bridge. The switching elements S1 and S4, and the switching elements S2 and S3, are alternately turned ON and OFF, and thereby an alternating current flows in the primary winding of the output transformer (refer to Patent Document #1).
In the half bridge type, respective voltage sources C1 and C2 are connected in parallel to switching elements S1 and S2, and a power supply V is connected between the voltage sources C1 and C2. The switching elements S1 and S2 are alternately turned ON and OFF, and thereby an alternating current flows in the primary winding P (refer to Patent Document #2).
In the center tap push-pull type, a power supply V is connected to a center tap of a primary winding P that is connected between switching elements S1 and S2. The switching elements S1 and S2 are alternately turned ON and OFF, and thereby an alternating current flows in the primary winding P (refer to Patent Document #3).